Gaseous reference materials to underpin measurements of amount - PowerPoint PPT Presentation

Gaseous reference materials to underpin measurements of amount fraction and isotopic composition of greenhouse gases Paul Brewer NOAA ESRL Global Monitoring Annual Conference 23 rd May 2017

Rationale Requirement for traceability from the primary realisation of the mole • Legislation aimed at reducing emissions and their measurement • Long-term observations based on accurate and stable standards • 10 carbon emissions (billion tons per year) 440 Carbon Dioxide (parts per million) 9 420 8 Population (billion) 7 400 6 380 5 360 4 400 ± 0.05 µ mol/mol 3 340 400 ± 0.10 µ mol/mol 0.025 % 2 320 0.031 % 325 ± 0.1 nmol/mol 1 1800 ± 2 nmol/mol 0.10 % 300 0 1920 1950 1980 2010 7 ± 0.02 pmol/mol 0.67 % 300 ± 2 nmol/mol

Comparability CO 2 2006 CO 2 2013 CH 4 2003 Isotopic composition of 12 CO2 - 13 CO2 2013 • matched to natural abundance Uncertainty < 0.05 % for CO 2 and < 0.1 • % for CH 4 (k=1)

Synthetic Reference Standards Gravimetric preparation • Purity analysis • Analytical validation • Challenges Purity and gravimetry Stability Commutability

Purity and gravimetry New method with lower uncertainty • NPL Adjustable Gas Standard • Quantification by standard addition •

Stability amount fraction change (µmol/mol) 10 weeks 20 30

Commutability Influence of matrix composition • on spectroscopy (requirement for 0.1 cmol mol -1 ) More pronounced for CO 2 • H. Nara, H. Tanimoto, Y. Tohjima, H. Mukai, Y. Nojiri, K. Katsumata and C. W. Rella, Atmos. Meas. Tech. , 5 , 2689–2701, (2012). 1 ‰ corresponds to ~ 4 nmol/mol

Commutability fermentation natural gas NPL blend combustion

Calibration 636 626 628 628 628

Influence of the calibration W C B F -1 ‰ -5 ‰ -11 ‰ -35 ‰

Metrology for Stable Isotope Reference Standards (SIRS) The project will address: Limitations in infrastructure to deliver international gaseous CO 2 reference materials • Absence of international gaseous N 2 O reference materials with stated uncertainties • Advances in optical spectroscopy for traceable field deployable techniques • New reference materials, calibration methods and instrumentation CO 2 (pure and 400 µmol/mol in air, uncertainties: δ 13 C-CO 2 0.1 ‰, δ 18 O-CO 2 0.5 ‰) • Re-measure absolute CO 2 isotope ratios to provide data for SI traceability • N 2 O (pure and 300 – 1000 nmol/mol in air) • reference materials (uncertainties 1.0 ‰ ( δ 15 N α and δ 15 N β ) and 0.5 ‰ ( δ 15 N, δ 18 O)) Spectroscopic methods for isotope ratio • measurements

Conclusions Substantial progress made towards developing an infrastructure to provide SI traceability for • measurements of CO 2 , CH 4 , N 2 O and CO Research required to deliver gaseous reference materials for isotope ratio of CO 2 and N 2 O • Acknowledgements